Epidemiology Of Varicella Research Articles

Impact of a 2-dose voluntary vaccination strategy on varicella epidemiology in Beijing, 2011–2017

BackgroundOne-dose voluntary varicella vaccination for children was introduced in Beijing since 1998. In Oct 2012, a second dose varicella vaccine (VarV) was recommended to further decrease varicella disease and the outbreaks. We describe the impact of the 2-dose voluntary vaccination strategy on varicella epidemiology in Beijing, China. MethodsVaricella incidence rates and outbreak characteristics in 2011–2017 was examined using surveillance data. Varicella vaccination coverage among children born in 2007–2012 was estimated through Beijing children immunization registry system. Vaccine effectiveness (VE) for VarV2 was estimated by screening method. ResultsOverall varicella incidence decreased by 37.8% from 103.2 per 100,000 population in 2011 to 64.2 per 100,000 population in 2017. Incidence declines in children aged <15 years with most significantly decrease by 82.3% in children aged 5–9 years, while no significant change happened in adolescent and adults. A total of 251 outbreaks with 3239 outbreak-related cases were reported in 2011–2017, the number of outbreaks decreased significantly by 50.7% from 69 in 2011 to 34 in 2017. The VarV1 coverage ranged from 85.4% to 92.6% among children 4 year of age and the VarV2 coverage ranged from 40.1% to 72.9% among children 6 year of age in the 2007–2012 birth cohort. Overall VE estimates against all varicella disease was 94.4% (95% CI: 89.9–98.9%) for VarV2. ConclusionsModerate VarV2 coverage has been achieved in Beijing resulting in remarkable declining of the incidence in children. Varicella outbreaks has not been eliminated suggested that measures such as including a 2-dose varicella vaccination in routine immunization program should be taken in the future.

The impact of long-term moderate level of vaccination coverage for epidemiology of varicella in Lu'an, China: should we change immunisation strategy now?

As China implements the voluntary vaccination programme of one-dose of varicella vaccine (VarV) for decades, robust estimates of the impact of voluntary vaccination era on epidemiology of varicella are needed. We estimated the vaccination coverage (VC) of VarV by using surveillance data on immunisation. The descriptive epidemiological method was used to describe the changing epidemiology of varicella from 2007 to 2018. The screening method was used to estimate the vaccine effectiveness (VE) of VarV. The overall VC for VarV was 71.7%, ranged from 47.7% to 79.5% among 2008-2017 birth cohorts. In total, 16 660 varicella cases were reported during 2007-2018, the incidence increased from 10.0 cases per 100 000 population in 2007 to 65.2 cases per 100 000 population in 2018. A shift in age group of varicella was observed since 2012, with the age increased from 5-9 years to 10-14 years. The overall VE was 79.9%, and the VE increased from 60.1% in 2008 birth cohort to 96.2% in 2017 birth cohort. We found that the overall VE for VarV is moderate, but appears highly effective within 5 years after vaccination. In addition, a shift varicella infection to older ages has occurred at the long-term moderate level VC of one-dose VarV. Therefore, to contain the incidence of varicella and prevent any potential shift to older ages, the introduction of VarV into routine immunisation programme is likely needed in Lu'an.

Spatiotemporal Epidemiology of Varicella in Chongqing, China, 2014–2018

Although immunization against varicella using vaccines has been proven to be significant and effective in the past decades, varicella remains a major public health concern for many developing countries. Varicella vaccination has not been introduced into routine immunization programs in China, and varicella outbreaks have continued to occur. Taking the city of Chongqing, which has a high prevalence of varicella, as an example, this study explored the spatiotemporal epidemiology of varicella. Based on the reported data of varicella cases from 1 January 2014 to 31 December 2018 in Chongqing, hot spots and space-time clusters of varicella were identified using spatial autocorrelation analysis and scan statistics. Within this period, a total of 112,273 varicella cases were reported in Chongqing (average annual incidence: 73.44 per 100,000), including one death. The incidence of varicella showed an increasing trend with significant seasonal peaks, which occurred during April to July and October to January of the following year. The total ratio of male to female patients affected was 1.10:1. Children under the age of 15 and students accounted for the majority of the patient population. The hotspots detected through local spatial autocorrelation analysis, and the most likely clusters identified by scan analysis, were primarily in the main urban districts of Chongqing. The secondary clusters were mostly detected in northeast and southwest Chongqing. There were obvious spatial dependence and spatiotemporal clustering characteristics of varicella in Chongqing from 2014 to 2018. High-risk districts, populations, and peak periods were found in this study, which could be helpful in implementing varicella prevention and control programs, and in adjusting vaccination strategies for the varicella vaccine based on actual conditions.

Budget impact analysis of multiple varicella vaccination strategies: a Mexico perspective

ABSTRACT A number of live-attenuated varicella vaccines are produced globally that provide protection against the varicella zoster virus. In Mexico, varicella vaccination is not included in the national immunization program and is recommended for use only in high-risk subgroups. We developed a budget impact model to estimate the impact of universal childhood immunization against varicella on the national payer system in Mexico. A scenario of no varicella vaccination was compared to scenarios with vaccination with a single dose at 13 months of age, in alignment with the existing program of immunization with the measles-mumps-rubella vaccine. Nine different vaccination scenarios were envisioned, differing by vaccine type and by coverage. Varicella cases and treatment costs of each scenario were computed in a dynamic transmission model of varicella epidemiology, calibrated to the population of Mexico. Unit costs were based on Mexico sources or were from the literature. The results indicated that each of the three vaccine types increased vaccine acquisition and administration expenditures but produced overall cost savings in each of the first 10 years of the program, due to fewer cases and reduced varicella treatment costs. A highly effective vaccine at 95% coverage produced the greatest cost savings.

Reply letter: trends in varicella and herpes zoster epidemiology before and after the implementation of universal one-dose varicella vaccination over one decade in South Korea, 2003-2015

ABSTRACTIn the letter, Lai SW suggested that the cost-benefit of two-dose varicella vaccines should be considered since universal one-dose vaccination effectively reduced varicella incidence in Taiwan. However, the vaccination impact was different between South Korea and Taiwan. In South Korea, only a moderate reduction in varicella incidence was observed after implementing universal one-dose vaccination. Such difference possibly reflects the relatively high background varicella incidence in South Korea. As substantial variability in varicella epidemiology exists across countries, an optimal vaccination strategy may differ in each country. Despite the effectiveness of one-dose vaccine being moderate, primary vaccine failure and rapidly waning immunity are major concerns. Therefore, two-dose vaccination would be a reasonable choice for effectively preventing virus transmission in South Korea.

Trends in varicella epidemiology before and after the implementation of universal one-dose varicella vaccination

Recently one cohort study conducted by Choi et al published in Human vaccines & immunotherapeutics demonstrated that the incidence rate of varicella decreased 67% after universal one-dose varicella...

Varicella in Tshuapa Province, Democratic Republic of Congo, 2009-2014.

To describe varicella cases in Tshuapa Province of the Democratic Republic of the Congo identified during monkeypox surveillance. Demographic, clinical and epidemiological data were collected from each suspected monkeypox case 2009-2014. Samples were tested by PCR for both Orthopoxviruses and varicella-zoster virus (VZV); a subset of VZV-positive samples was genotyped. We defined a varicella case as a rash illness with laboratory-confirmed VZV. There were 366 varicella cases were identified; 66% were ≤19 years old. Most patients had non-typical varicella rash with lesions reported as the same size and stage of evolution (86%), deep and profound (91%), on palms of hands and/or soles of feet (86%) and not itchy (49%). Many had non-typical signs and symptoms, such as lymphadenopathy (70%) and sensitivity to light (23%). A higher proportion of persons aged ≥20 years than persons aged ≤19 years had ≥50 lesions (79% vs. 65%, P = 0.007) and were bedridden (15% vs. 9%, P = 0.056). All VZV isolates genotyped from 79 varicella cases were clade 5. During the surveillance period, one possible VZV-related death occurred in a 7-year-old child. A large proportion of patients presented with non-typical varicella rash and clinical signs and symptoms, highlighting challenges identifying varicella in an area with endemic monkeypox. Continued surveillance and laboratory diagnosis will help in rapid identification and control of both monkeypox and varicella and improve our understanding of varicella epidemiology in Africa.

Trends in varicella and herpes zoster epidemiology before and after the implementation of universal one-dose varicella vaccination over one decade in South Korea, 2003–2015

ABSTRACTBackground: In South Korea, the one-dose varicella vaccine was included in the National Immunization Program for children aged 12–15 months in 2005, and the vaccine coverage reached >95%. The impact of varicella vaccination on varicella and herpes zoster (HZ) was investigated, accounting for demographic changes over time.Methods: We calculated the crude and age-sex standardized incidence rates (IRs) and age-specific IRs of varicella and HZ from 2003 to 2015, using the National Health Information Database including approximately 50 million Koreans. The annual incidence rate ratios (IRRs) were calculated using a negative binomial regression analysis, adjusting for age and sex.Results: The crude varicella IR steadily declined by 67%, from 5.70/1000 to 1.87/1000 person years (IRR per year: 0.91; 95% CI 0.89–0.93), but the adjusted IRs showed a significant decline only during 2010–2015 (adjusted IRR per year: 0.90; 95% CI 0.88–0.93). The greatest decline was found in children ≤4 years of age, whereas the IR increased until 2011 and then declined afterward in children aged 5–9 years, who represented the highest incidence age group in 2013–2015. The crude HZ IR increased from 2.67/1000 to 9.80/1000 person years (IRR per year: 1.12; 95% CI 1.10–1.15), and the adjusted IR also followed the same trend. A similar increasing trend was observed before and after universal vaccination.Conclusions: One-dose varicella vaccination was moderately effective in preventing varicella, but this strategy was insufficient to interrupt varicella transmission in children. Furthermore, the HZ incidence dramatically increased over this decade. The current vaccination strategy against varicella-zoster disease should be reconsidered.

Descriptive epidemiology of varicella based on national surveillance data before and after the introduction of routine varicella vaccination with two doses in Japan, 2000–2017

Routine childhood immunization using two doses of the varicella vaccine was introduced in Japan in October 2014. In this study, we analyzed the data extracted from national varicella surveillance, including pediatric sentinel surveillance from 2000 to 2017 and hospitalized varicella surveillance from the 38th week of 2014 to the 37th week of 2017. Compared with the 2000–2011 baseline data, the number of varicella cases per sentinel decreased substantially by 76.6% overall and by 88.2% among children aged 1–4 years in 2017. Of 997 hospitalized patients, we found a decreasing trend in the number of cases among children aged <5 years. We also found a decreasing trend in the number of cases with complications among children aged 1–4 years. Data on the self-reported transmission sites in 35.5% (354/997) of the hospitalized varicella patients showed that transmission of varicella zoster virus (VZV) occurred frequently in household, at school for young children, in the workplace for adults, and at hospital for all age groups. Data from 29.0% (289/997) of the hospitalized patients with a self-reported source of infection showed that transmission of VZV occurred from a patient with herpes zoster (HZ) in 30.4% (88/289) of cases. Our data demonstrate a substantial decrease in the number of varicella cases in young children following introduction of routine childhood vaccination program with two-dose varicella vaccination in Japan. These data highlight the unique aspects of transmission sites across age groups and the important role of HZ cases in disease circulation.

The impact of demographic changes, exogenous boosting and new vaccination policies on varicella and herpes zoster in Italy: a modelling and cost-effectiveness study

BackgroundThe present study aims to evaluate the cost-effectiveness of the newly introduced varicella and herpes zoster (HZ) vaccination programmes in Italy. The appropriateness of the introduction of the varicella vaccine is highly debated because of concerns about the consequences on HZ epidemiology and the expected increase in the number of severe cases in case of suboptimal coverage levels.MethodsWe performed a cost-utility analysis based on a stochastic individual-based model that considers realistic demographic processes and two different underlying mechanisms of exogenous boosting (temporary and progressive immunity). Routine varicella vaccination is given with a two-dose schedule (15 months, 5–6 years). The HZ vaccine is offered to the elderly (65 years), either alone or in combination with an initial catch-up campaign (66–75 years). The main outcome measures are averted cases and deaths, costs per quality-adjusted life years gained, incremental cost-effectiveness ratios, and net monetary benefits associated with the different vaccination policies.ResultsDemographic processes have contributed to shaping varicella and HZ epidemiology over the years, decreasing varicella circulation and increasing the incidence of HZ. The recent introduction of varicella vaccination in Italy is expected to produce an enduring reduction in varicella incidence and, indirectly, a further increase of HZ incidence in the first decades, followed by a significant reduction in the long term. However, the concurrent introduction of routine HZ vaccination at 65 years of age is expected to mitigate this increase and, in the longer run, to reduce HZ burden to its minimum. From an economic perspective, all the considered policies are cost-effective, with the exception of varicella vaccination alone when considering a time horizon of 50 years. These results are robust to parameter uncertainties, to the two different hypotheses on the mechanism driving exogenous boosting, and to different demographic projection scenarios.ConclusionsThe recent introduction of a combined varicella and HZ vaccination programme in Italy will produce significant reductions in the burden of both diseases and is found to be a cost-effective policy. This programme will counterbalance the increasing trend of zoster incidence purely due to demographic processes.

Epidemiology and factors influencing varicella infections in tropical countries including Sri Lanka.

Varicella zoster virus (VZV) infections occur worldwide but the epidemiology differs between different geographical regions. Epidemiology of varicella is partly understood in tropical and subtropical regions. Various hypotheses showing differences in exposure rates in different age groups have been proposed. Exposure to VZV during late childhood or adolescent stage causes high morbidity, especially in high school children, university students and young work force in tropical nations. Exposure to VZV infection or sero-prevalence rates through anti-VZV immunoglobulin G appears to be lower in Sri Lanka, similar to other tropical countries prior to the millennium. In contrast, a more recent study in a group of antenatal women showed a relatively higher exposure rate to VZV when compared to the exposure rates prior to 2004 in Sri Lanka. Climatic factors, socioeconomic conditions, mobility and cultural practices appear to play a role in the differences in the exposure rates to VZV infection in the tropics. In most tropical Asian countries including Sri Lanka, routine vaccination against varicella is not carried out. Individuals with negative history for varicella take the vaccine when there is a necessity. Medical and nursing students take the vaccine prior to their clinical training to avoid adulthood varicella.

Epidemiology, management and outcome of varicella in pregnancy: a 20-year experience at the Tuscany Reference Centre for Infectious Diseases in Pregnancy.

Data from 215 pregnant women exposed to varicella and 276 with varicella observed at the Tuscany Reference Center for Infectious Diseases in Pregnancy, Florence, Italy, in the period 1997-2016 were retrospectively collected. The risk of developing varicella was lower in exposed women who received varicella zoster immunoglobulin compared with those who did not receive it [42% (21 of 50) vs 72% (13 of 18); p = 0.0263]. Typical congenital varicella syndrome was observed in 1.56% of fetuses/neonates born from pregnant women with varicella.

The changing epidemiology of varicella and herpes zoster in Hong Kong before universal varicella vaccination in 2014.

In Hong Kong, universal varicella vaccination started in July 2014. Before this, children could receive varicella vaccine via the private market. We analysed the epidemiology of varicella and zoster before universal vaccination. We estimated varicella vaccination coverage through surveys in preschool children. We estimated the burden of varicella and zoster with varicella notifications from 1999/00 to 2013/14, Accident and Emergency Department (A&E) attendance and inpatient admissions to public hospitals from 2004/05 to 2013/14. We fitted a catalytic model to serological data on antibodies against varicella-zoster virus to estimate the force of infection. We found that varicella vaccination coverage gradually increased to about 50% before programme inception. In children younger than 5 years, the annual rate of varicella notifications, varicella admission and zoster A&E attendance generally declined. The annual notification, A&E attendance and hospitalisation rate of varicella and zoster generally increased for individuals between 10 and 59 years old. Varicella serology indicated an age shift during the study period towards a higher proportion of infections in slightly older individuals, but the change was most notable before vaccine licensure. In conclusion, we observed a shift in the burden of varicella to slightly older age groups with a corresponding increase in incidence but it cannot necessarily be attributed to private market vaccine coverage alone. Increasing varicella vaccination uptake in the private market might affect varicella transmission and epidemiology, but not to the level of interrupting transmission.

Varicella Outbreak Surveillance in Schools in Sentinel Jurisdictions, 2012-2015.

In 2007, a routine second dose of varicella vaccine was recommended in the United States for children aged 4 to 6 years to better control varicella-zoster virus circulation and outbreaks. Sentinel varicella outbreak surveillance was established to assess feasibility of surveillance and describe outbreaks that are occurring. Through the Centers for Disease Control and Prevention Epidemiology Laboratory Capacity funding, health departments conducted active surveillance for varicella outbreaks in schools from 2012 to 2015. Outbreaks of varicella were defined as ≥5 cases in a school within at least 1 incubation period (21 days). School nurses, healthcare providers, or laboratories reported cases and outbreaks of varicella to health departments; demographic, vaccination, and clinical data were collected. Georgia, Houston, Maine, Minnesota, New York City, and Philadelphia participated in all 3 years; Puerto Rico and West Virginia participated in 2012 to 2013; and Kansas and Arkansas participated in 2014 to 2015. Twenty-nine outbreaks including 262 cases were reported. The median size of the outbreaks was 7 cases (range, 5-31 cases), and the median duration was 31 days (range, 4-100 days). Of the case-patients associated with larger outbreaks (≥8 cases), 55.4% were unvaccinated, and 15.7% and 18.1% had received 1 or 2 doses of vaccine, respectively. In small outbreaks (5-7 cases), 33.3% of case-patients were unvaccinated, and 16.7% and 38.5% had received 1 or 2 doses of vaccine, respectively. The majority of cases associated with outbreaks occurred in undervaccinated children (unvaccinated and 1-dose vaccine recipients). Outbreaks with a greater proportion of 2-dose vaccine recipients were smaller. Varicella outbreak surveillance is feasible, and continued monitoring of outbreaks remains important for describing the epidemiology of varicella during the 2-dose varicella vaccination program.

Influence of demographic changes on the impact of vaccination against varicella and herpes zoster in Germany \u2013 a mathematical modelling study

BackgroundEpidemiological studies suggest that reduced exposure to varicella might lead to an increased risk for herpes zoster (HZ). Reduction of exposure to varicella is a consequence of varicella vaccination but also of demographic changes. We analyzed how the combination of vaccination programs and demographic dynamics will affect the epidemiology of varicella and HZ in Germany over the next 50 years.MethodsWe used a deterministic dynamic compartmental model to assess the impact of different varicella and HZ vaccination strategies on varicella and HZ epidemiology in three demographic scenarios, namely the projected population for Germany, the projected population additionally accounting for increased immigration as observed in 2015/2016, and a stationary population.ResultsProjected demographic changes alone result in an increase of annual HZ cases by 18.3% and a decrease of varicella cases by 45.7% between 1990 and 2060. Independently of the demographic scenario, varicella vaccination reduces the cumulative number of varicella cases until 2060 by approximately 70%, but also increases HZ cases by 10%. Unlike the currently licensed live attenuated HZ vaccine, the new subunit vaccine candidate might completely counteract this effect. Relative vaccine effects were consistent across all demographic scenarios.ConclusionDemographic dynamics will be a major determinant of HZ epidemiology in the next 50 years. While stationary population models are appropriate for assessing vaccination impact, models incorporating realistic population structures allow a direct comparison to surveillance data and can thus provide additional input for immunization decision-making and resource planning.

Varicella infection in a non-universally vaccinated population: Actual epidemiology in Bulgaria (2013-2015).

Varicella is a common and usually mild disease but it has great importance in regard to general infectious morbidity. The current study aimed to characterize possible risk factors of varicella epidemiology in Bulgaria, a country where infection follows its natural epidemiological pattern as no mandatory or recommended vaccine is currently applied. Administrative regions of Bulgaria were used as units of observation and a set of sociodemographic and economic determinants, as well as geographic location (south or north) were tested for associations with the mean 3-year varicella incidence rates (2013-2015). The proportion of urban population, proportion of females, number of health care units and proportion of urban population aged <10 years were the four sociodemographic variables most strongly and significantly correlated (p<0.05) with varicella frequency (Spearman's rank correlation coefficients of 0.62, 0.47, 0.43, and 0.38, respectively). After reducing the number of intercorrelated factors to a few principal components and accounting for confounders, the demographic component and geographic location remained most robustly associated with varicella incidence in Bulgaria (adjusted R2 of 0.51, p<0.001). The results obtained identify important determinants in the local epidemiology of varicella and show that community characteristics should be considered, to improve our understanding of varicella distribution.

A systematic review of varicella seroprevalence in European countries before universal childhood immunization: deriving incidence from seroprevalence data.

Surveillance systems for varicella in Europe are highly heterogeneous or completely absent. We estimated the varicella incidence based on seroprevalence data, as these data are largely available and not biased by under-reporting or underascertainment. We conducted a systematic literature search for varicella serological data in Europe prior to introduction of universal varicella immunization. Age-specific serological data were pooled by country and serological profiles estimated using the catalytic model with piecewise constant force of infection. From the estimated profiles, we derived the annual incidence of varicella infection (/100·000) for six age groups (<5, 5-9, 10-14, 15-19, 20-39 and 40-65 years). In total, 43 studies from 16 countries were identified. By the age of 15 years, over 90% of the population has been infected by varicella in all countries except for Greece (86·6%) and Italy (85·3%). Substantial variability across countries exists in the age-specific annual incidence of varicella primary infection among the <5 years old (from 7052 to 16 122 per 100 000) and 5-9 years old (from 3292 to 11 798 per 100 000). The apparent validity and robustness of our estimates highlight the importance of serological data for the characterization of varicella epidemiology, even in the absence of sampling or assay standardization.

Role of meteorological conditions in reported chickenpox cases in Wuhan and Hong Kong, China

BackgroundChickenpox is a common contagious disease that remains an important public health issue worldwide. Over 90% of unvaccinated individuals become infected, but infection occurs at different ages in different parts of the world. Many people have been infected by 20 to 30 years of age in China, and adults and pregnant women who become infected often develop severe infection. Furthermore, a mortality rate of 2–3 per 100,000 infected persons has been reported. In this study, we explore the temperature-dependent transition of patterns of reported chickenpox cases in two large subtropical climate cities, Wuhan and Hong Kong, China, to aid in the prediction of epidemics and preparation for the effects of climatic changes on epidemiology of chickenpox in China.MethodsWe used a time series analysis comprising a spectral analysis based on the maximum entropy method in the frequency domain and the nonlinear least squares method in the time domain. Specifically, the following time series data were analyzed: data of reported chickenpox cases and meteorological data, including the mean temperature, relative humidity and total rainfall in Wuhan and Hong Kong from January 2008 to June 2015.ResultsThe time series data of chickenpox for both Wuhan and Hong Kong have two peaks per year, one in winter and another in spring, indicating a bimodal cycle. To investigate the source of the bimodal cycle of the chickenpox data, we defined the contribution ratio of the 1-year cycle, Q1, and the 6-month cycle, Q2, as the contribution of the amplitude of a 1-year cycle and a 6-month cycle, respectively, to the entire amplitude of the time-series data. The Q1 values of Wuhan and Hong Kong were positively correlated with the annual mean temperature and rainfall of each city. Conversely, the Q2 values of Wuhan and Hong Kong were negatively correlated with the annual mean temperature and rainfall of Wuhan and Hong Kong.ConclusionOur results showed that the mean temperature and rainfall have a significant influence on the incidence of chickenpox, and might be important predictors of chickenpox incidence in Wuhan and Hong Kong.

Epidemiology of varicella in Haidian district, Beijing, China—2007–2015

Background1-Dose varicella vaccination was recommended for children in Beijing before November 2012. To further control school-based outbreaks and decrease incidence, a 2-dose vaccination was implemented in 2013. We described the varicella epidemiology and assessed impact of the 2-dose vaccination in Haidian district, Beijing, 2007–2015. MethodsWe examined the estimated incidence and disease characteristics of varicella during 2007–2015 and obtained the 1-dose vaccination coverage for children born during 2005–2013. Number of vaccine doses given was used to indirectly reflect the second-dose vaccination coverage. Overall and age-specific estimated incidences were compared between 2007–2012 and 2013–2015. ResultsA total of 23,497 cases were reported during 2007–2015. Of the 23,497 cases, 13,440 (57.20%) were male, and 68.40% were <20years of age and 70.02% were students and children in kindergarten. The estimated incidence increased from 82 cases per 100,000 population in 2007 to 104 in 2011, before substantially decreasing from 86 in 2012 to 56 in 2015. The median age increased from 14years in 2007 to 18years in 2015. The 1-dose varicella coverage for children at ≥2years of age gradually increased from 74.21% in 2007 to 90.06% in 2015. Compared with 2007–2012, two-fold average vaccine doses were given during 2013–2015, and the overall estimated incidence declined by 34.4%, particularly in children aged 5–9years, with a significantly declined trend in children aged 1–9years and older adolescents aged 15–19years and non-significantly declined trend in adults aged ≥20years, but a significant increasing trend in infants. ConclusionsThe overall incidence of varicella has decreased substantially in Haidian district since 2013, with largest decline in children aged 5–9years. The 2-dose varicella vaccination might not lead to increase in incidence in adults. Long-term surveillance is needed to fully evaluate the long-term impact of the 2-dose varicella vaccination.

The economic impact of prenatal varicella immunity among pregnant women in Alberta

In light of the changing epidemiology of varicella, we sought to examine varicella antibody levels in the prenatal population in the Canadian province of Alberta. All prenatal varicella screening tests performed between August 1, 2002 and February 2, 2014 (454,592) were included in this study. Test results, demographics and vaccination status were examined to identify varicella seroprevalence and correlates for being seronegative. An overall seroprevalence for varicella of 95.8% was found across all pregnancy screenings. Significant independent correlates of seronegativity included younger age (AOR: 4.72 (95% CI: 3.87–5.77) for <20years of age vs. >40years of age) and having immigrated to Alberta from Africa or Asia (AOR: 4.55 (95% CI: 4.10–5.05) and AOR: 5.83 (95%CI; 5.48–6.19), respectively). Women who were initially seronegative for varicella antibodies and who received both postnatal vaccination and post-vaccination prenatal screening (2566) were examined to assess seroconversion. 66.3% of women who were tested up to six months post-vaccination were seropositive, however only 36.9% of women tested after 36months were seropositive. Finally, 40.9% of all prenatal varicella specimens tested were deemed redundant, i.e. women had either a history of (1) ⩾2 doses of varicella vaccine, (2) varicella infection, or (3) a previous positive varicella serology. Eliminating this redundant screening could provide an estimated $96,000 in savings annually in laboratory and Public Health follow-up costs alone. As the number of women with vaccine-derived immunity through universal childhood vaccination increase in the prenatal population, screening methods may need to adapt to ensure varicella immunity is accurately conducted and assessed.